The present disclosure relates to a colorimetric sensor material in which one-dimensional polymer nanofiber is coupled to fine dye particles generating color change when the dye particles are exposed to a specific gas, a gas sensor, and a method of the same. More particularly, in a method of manufacturing an electrospinning solution, after a dye is stirred at a high temperature of more than melting point to be liquefied, the liquefied dye may be quenched to control crystal growth which is generated in a dry process at room temperature, and dye particles for detecting hydrogen sulfide gas may be formed in which the dye particles finely dispersed by a polymer dissolved in a solvent, without a mass. A polymer nanofiber sensor for detecting hydrogen sulfide having high porosity and a high surface area, in which an electrospinning solution dispersed fine lead acetate particles performs an electrospinning process such that the fine dye particles are coupled to an inner part and a surface of an one-dimensional polymer fiber while each having a biconvex lens shape, in which a ratio of a long axis to a short axis is more than 1, and a method of manufacturing the same may be provided.
Various noxious gases are used across industrial technology. A gas sensor having a high sensitivity and fast response are necessary to monitor a noxious gas leak generated at a work area for preventing a severe accident or damage for humans. In additional, a gas sensor may be used for measurement of a degree of air pollution and measurement of air quality of a room as air pollution becomes serious due to industrialization.
In recent, an exhalation sensor for health care capable of easily diagnosing a specific disease by detecting a biomarker gas in exhalation of respiration is studied. Various biomarker gases such as hydrogen sulfide, pentane, toluene, acetone, nitrogen monoxide, and ammonia are generated by reaction of cells of a human body through respiration and are discharged through respiration. It is reported that these gases function as biomarkers for halitosis, cardiac disease, a lung cancer, diabetes, and kidney disease. Since hundreds of various gases are blended in exhalation, a specific biomarker should be selectively detected. Furthermore, since the biomarker gas of exhalation is discharged at a low concentration having a range of 10 part per billion (ppb) to 10 part per million (ppm), a gas sensor having high sensitivity for precisely detecting the gas having a concentration of 10 ppb should be developed.
The gas sensor may be mainly classified into a gas chromatography, a variable resistance gas sensor, and a colorimetric gas sensor based on a gas detection operation manner. In the gas chromatography, a specimen is injected into an inlet such that evaporation occurs and the evaporated material is separated by columns of the gas chromatography. Compound components of the separated gas phase are displayed at a monitor using an electric signal proportional to the amount of the detected gas through a detector. The gas chromatography performs a precisely quantitative analysis but is expensive and has a large size such that it is improper to be portable. Furthermore, the variable resistance gas sensor based on a metal oxide semiconductor detects a specific gas, in which adsorption-desorption of the specific gas on the metal oxide semiconductor generates variable resistance such that the specific gas is detected. The variable resistance gas sensor has simple sensor system constitutions and is easy to carry but has low sensitivity and selectivity, in comparison with the gas chromatography. Meanwhile, the colorimetric sensor capable of visually detecting color change when being exposed to the specific gas is studied. In the colorimetric sensor, when a material used as a dye reacts with a specific gas, the reaction influences a band structure of the material such that an absorption wavelength of a visible light is changed while color change occurs. In addition, an analyte gas may be detected through a colored product generated by reaction of the analyte gas and the dye. Moreover, the colorimetric sensor does not need additional circuit designing and measuring equipment and has a test paper shape, thereby being portable. However, gas sensitivity and selectivity are less than the gas chromatography and the variable resistance gas sensor.
Various nanostructures are developed for development of a colorimetric sensor having high sensitivity. Since a detecting material based on a nanostructure such as a nanoparticle, a nanofiber, a nanotube, and a nano-hollow structure has a large area in comparison to an existing material such as a thick film, superior gas detecting properties may be provided. Particularly, since the colorimetric sensor generates color change by a surface reaction of the dye material and the analyte gas, reacting sites, in which gas particles are in contact with the dye material, are increased by application of the nanostructures such that gas sensitivity can be improved. lead(II) acetate (Pb(CH3COO)2)) includes an anhydrous state and a trihydrate state in natural. lead(II) acetate anhydrous has the melting point of 280° C. and lead(II) acetate trihydrate has the melting point of 75° C. The above two states of lead acetate have already been used as a dye capable of selectively detecting hydrogen sulfide in a film type in an industrial field to monitor leak of hydrogen sulfide. The colorimetric sensor is used when lead(II) acetate reacts with the hydrogen sulfide (H2S) to form brown lead sulfide (PbS). However, there is a detection limit of 5 ppm such that hydrogen sulfide gas of less than 1 ppm is not detected. Hydrogen sulfide, i.e. a biomarker of a halitosis patient, has a concentration range of 50 ppb to 80 ppb in exhalation of a normal human but hydrogen sulfide has 1 ppm to 2 ppm in exhalation of a halitosis patient. However, since a teat paper for detecting hydrogen sulfide in market has poor sensitivity, it is impossible to diagnose halitosis due to low concentration of hydrogen sulfide.
Accordingly, it is necessary to develop a colorimetric sensor material having a large surface area for providing a maximum reaction area capable of being in contact with an analyte gas. In the case of a colorimetric sensor having a thick film type, gas molecules are not diffused into a detecting material due to absence of pores such that reaction is limited to a surface of the detecting material. For improvement of gas sensitivity, a colorimetric sensor in a porous structure is developed such that the gas molecules can react with the dye in an inner part as well as the surface reaction. Particularly, in the case of lead(II) acetate, after lead(II) acetate is dissolved, recrystallization growth occurs to have a size between several micrometers and tens-of-micrometer such that it is important to secure process technology in which there is fine crystal distribution in recrystallization growth for obtaining a high specific surface area.